Method for producing polyamide filamentary article



Dec. 1, 1970 TAHCHIMURAO m v 3,544,570

METHOD FOR PRODUCING POLYAMIDE FILAMENTARY ARTICLE Filed Sept. 5, 1968 2 Sheets-Sheet 1 V144 TER COOL/N6 60 5 %Na0H AQUEOUS SOLUTION (25 c) SATURA 7E0 NaOH AQUEOUS SOLUTION (25C) REFLECTANCE(% Q Kn 9 Q Q WAVELENGTH (my United States Patent 3,544,670 METHOD FOR PRODUCING POLYAMIDE FILAMENTARY ARTICLE Taiichi Murao, Masakatsu Hara, Toru Sato, and Shigeo Katsuyama, Nobeoka-shi, and Toshio Sasaki, Ibaragishi, Japan, assignors to Asahi Kasei Kogyo Kabushiki Kaisha, Osaka, Japan, a Japanese corporation Filed Sept. 5, 1968, Ser. No. 757,681 Claims priority, application Japan, Sept. 12, 1967, 42/58,093 Int. Cl. D01d 5/08 US. Cl. 264-178 7 Claims ABSTRACT OF THE DISCLOSURE A polyamide filamentary article having high trans parency and gloss is produced by solidifying a meltextruded polyamide with a solution of an alkali such as KOH, NaOH and LiOH.

This invention is concerned with the preparation of polyamide filamentary articles such as nylon 6, nylon 66 and nylon 610 which has high gloss and transparency and which is suitable for fishing net, fishing line or sewing thread, wherein an alkali solution is used as a cooling bath in melt-spinning a polyamide such as nylon 6, nylon 66 and nylon 610 and cooling same.

Various methods have been proposed for producing transparent polyamide filamentary articles used for fishing net, fishing lines or sewing thread. For example, there has been proposed a method according to which a melt-spun polyamide filamentary article is solidified b rapidly cooling it using cold water or an aqueous solution of salts as a cooling medium. However, according to such a method, the transparency of the resultant product is not improved unless the temperature of the cold water or the aqueous solution of salts is lowered.

Further, it is known that a melt-spun polyamide filamentary article is cooled and solidified using methanol or trichloroethylene at a temperature of -5 to 60 C. as a cooling medium. However, according to this method, the opaqueness of the filament surface can be removed due to the use of the specific organic liquid which is used as a cooling medium, but the said organic liquid is less effective in removing the inside spherulite which causes opaqueness within the filaments than is water because of the low thermal conductivity and specific heat. Thus, such method is not very effective on monofilaments of large diameter. Further, a great heat loss is caused in order to maintain a low temperature of from 5 to -60 C. Moreover, since the organic liquid used is volatile at high temperatures, the loss of the liquid is great and the vapor of the liquid is harmful to the human body and thus pollutes the atmosphere during the operation. Therefore, complicated apparatus is required, thereby making the operation difficult. Thus, the method has economic disadvantages.

Another method is known which uses Water or an aqueous solution of salts on which a non-polar liquid such as liquid paraffin is floated as a cooling medium for cooling and solidifying the melt-spun polyamide filaments. This method has economic disadvantages because the liquid paraffin floating on water or the aqueous solution of salts adheres to the surface of the filament, whereby the guide or drawing roller used in the operation is contaminated and a further step for removing the liquid paraffin adhering to the filaments is thus required. In addition, satisfactory transparency of the resultant product was not obtained.

A method in which a polyamide is mixed with a higher 3,544,670 Patented Dec. 1, 1970 aliphatic acid such as stearic acid and behenic acid and is melt-spun is also known. However, in this method the additive cannot be homogeneously dissolved in the product and thus no homogeneous product is obtained. In a method which is an improvement upon the last mentioned method, e-caprolactam to which a straight chain saturated aliphatic carboxylic acid having 16-22 of carbon atoms is added is polymerized, the thus obtained polymer is mixed with a polyamide, and the mixture is melt-spun. However, such a method is not etfective for improving the transparency of filaments having a large diameter or films having a great thickness. In order to increase the efiects of the carboxylic acid added, a large amount of said acid must be added. However, the addition of a large amount of said acid results in a conspicuous reduction in spinnability, as a result of which, the product is difiicultly obtained.

Further, a method in which a polyamide to which barium stearate is added is spun is also known. However, the barium stearate added is also not effective unless it is added in a large amount. Thus, this method also has economic disadvantages.

There is also a known method according to which a melt-spun polyamide filamentary article is cooled and solidified with a phenol solution as a cooling medium to swell the surface of the filaments and prevent the deformation of filaments generated during the drawing step, to thereby improve the transparency of the filaments. Further, in a known method, a polyamide to which an alkanol amine and its derivatives are added is melt-spun to raise the crystallization speed of the polyamide to improve the transparency. However, these methods are not effective and their products are not satisfactory as goods which require a high degree of transparency.

The object of this invention is to provide a novel method which overcomes the defects in all the conventional methods mentioned above.

This invention will be explained in detail as follows.

The gist of this invention resides in the use of an aqueous solution of an alkali having a concentration of less than saturation as a cooling medium in cooling and solidifying a melt-spun polyamide such as nylon 6, nylon 66, and nylon 610. As the alkali solution, a base such as a hydroxide of an alkali, that is, KOH, NaOH, LiOH, etc. is preferably used, and so long as it is an alkali solution, the solution may additionally contain other salts.

The temperature of the solution is preferably lower than 50 C.

Further, the concentration of the alkali in the solution affects the transparency and the gloss degree of the product. The transparency and the gloss degree are reduced with a reduction of the concentration. Although the alkali limit of the concentration is not clear, a concentration of higher than 5% appears to be effective from the practical viewpoint.

When the polyamide filamentary article is cooled and solidified in an alkali solution and thereafter passed through a water-washing bath, the alkali which adheres to the surface of the filamentary article is dissolved in the water and is easily removed. The thusly treated filamentary article is thereafter subjected to the usual treatments and is then wound up.

According tod this invention, the alkali solution dissolving their salt also gives the same results.

The obtained polyamide filamentary article has high surface gloss and transparency and is soft without deterioration of the physical and chemical properties regardless of the shape of cross section of the filamentary article. In the drawings which show the comparisons of the properties of the polyamide filamentary article obtained by this method and those of the product obtained by the conventional method, FIG. 1 shows the curves of reflectance, FIG. 2 shows curves of bending stress transparency and the other properties as shown in the following table.

Elonga- Bending Transmit- Strength, tion, Whitestress, tance g./d. percent Denier ness Gloss g./d. percent Product obtained by water cooling (27 C.) 5. 11 26. 8 1, 069 58. 9 8. 9 0. 21X10- 6. Product of this invention 5. 24 29. 7 1, 078 63. 7 14. 1 0. 16X 10- 14. and FIG. 3 shows curves of gloss degree. Comparison of EXAMPLE 2 the reflectance curve in the area of visible light of the polyamide filamentary article of this invention with that of the conventional product obtained by solidifying with water shows that the product of this invention indicated by the solid line has a lower reflectance and better transparency than the conventional product indicated by a dotted line as is clear from FIG. 1. Regarding the bending stress in the direction of the axis of the filaments, FIG. 2 shows that the bending resistance curve of the product of this invention indicated by a solid line is much easier than Elonga- Bending Transmit- Strength, tion, Whitestress, tance, g./d. percent Denier ness Gloss g./d. percent Product obtained by water cooling (5 C.) 5. 41 30. 2 812 61. 3 8. 2 0. ISXIO- 7. 2 Product of this invention 5. 25. 3 798 55. 8 12. 8 0. 12X 10- 13. 6

that of the conventlonal product mdicated by a dotted EXAMPLE 3 line. That is, the bending resistance of the former is lower than that of the latter. This fact means that the product of. this invention displays a soft touch. Further,

regarding the gloss of the product, as is shown in FIG. 3,

the product of this invention has a remarkably high gloss degree.

As mentioned above, the polyamide filamentary article obtained by this invention has a conspiculously high transparency. The reason for such a result is not clear, but it seems that the molten and extruded polyamide filamentary article at a high temperature effects some reaction with the alkali metal to prevent the occurence of phe- Nylon 610 heated at 300 C. was melt-extruded through orifices of 0.8 m./m. under an extrusion pressure of atmospheric pressure. The resultant product was passed through a 30% aqueous NaOH solution at 10 C. to

Elonga- Bending Transmit- Strength, tion, Whitestress, tance g./d. percent Denier ness Gloss g./d. percent Product obtained by water cooling (10 C.) 4. 41 26. 1 920 78. 0 11. 6 0. 11X10- 6. 2 Product of this invention 4. 30 25. 3 935 71. 6 13. 2 0. 07X10- 10. 6

nomena such as the formation of spherullte whlch dam- EXAMPLE 4 ages the transparency of the filamentary article.

EXAMPLE 1 Nylon 6 heated at 280 C. was melt-extruded through regularly triangular orifices having a side of 0.54 m./m. under an extrusion pressure of 40 atmospheric pressure. The resultant extruded product was passed through a cooling bath (10 C.) which was a saturated aqueous Na SO solution in which 5% of NaOH was dissolved. The thusly obtained solidified product was passed through a waterwashing bath to remove the alkali adhering to the product, then cold-drawn to 3.8 times in air and wound up. The product was soft nylon monofilament excellent in transparency and gloss as shown in the following table.

Elonga- Bending Transmit- Strength, tion, Whltestress, tance,

g./d. percent Denier ness Gloss g./d. percent Product obtained by water cooling (2 C.) 4. 03 43. 0 53. 0 77. 7 11. 59 0. 29X10- 8 Product of this invention 4. 12 45. 8 50. 5 72. 3 14. 60 0. 12 (10- 11 EXAMPLE 5 ilsiellcted from the group consisting of KOH, NaOH and Y Q 5 heated at Was melt-extruded through 3. A method according to claim 1, wherein the poly- Slit orifices of 0.1 X m./m. under an extrusion pressure amide is a member selected from the group consisting of 40 atmospheric pressure. The extruded product Was of nylon 6, nylon 66, and nylon 610. passed through a 47% aqueous NaOH solution at 50 C. 5 4. A method according to claim 1, wherein the alkali Thus solidified product was passed through a watersolution additionally contains salts. washing bath to remove the alkali adhering to the prod- 5. A method according to claim 1, wherein the temuct, cold-drawn to 3.8 times in air and wound up. The perature of the alkali solution is lower than 50 C. product was soft nylon monofilament excellent in trans- 6. A method according to claim 4, wherein the alkali parency and gloss as shown in the following table. 0 solution contains Na SO Elonga- Bending Transmit- Strength, tion, Whitestress, tance,

g./d. percent Denier ness Gloss g./d. percent Product obtained by water cooling (50 C.) 4. 03 38. 5 350 50. 3 9. 3 0. 25 l0 6. 1

Product of this invention 3. 95 40. 5 375 45. 3 11. 5 0. 11X10' 8. 2

The values referred to in the above examples were 7. A method according to claim 6, wherein the alkali measured as follows: solution is saturated with respect to Na SO and has a concentration of 5% with respect to the alkali Strength-Elongation: These were obtained from tension SS curve. References Cited Whitenessgloss: 118 14-1013. UNITED STATES PATENTS id g stress: y a measuring apparatus of bending 2,324,397 7/1943 Hall 264 176UX R fl t 2 B H h t t 3,002,804 10/1961 Kilian 264181X 6 cc am a Spec 0 me er 3,027,602 4/1962 Hamilton et a1. 264178 What is claimed is; 3,318,989 5/1967 S810 et al. 264-176 1. A method for producing a highly transparent and glossy polyamide filamentary article, which comprises JULIUS FROME Primary Examiner cooling and solidifying a melt-spun polyamide using an I, H, WOO, Assistant Examiner alkali solution having a concentration of from 5% to less than saturation as a cooling medium. US. Cl. X.R.

2. A method according to claim 1, wherein said alkali 284237 

